Electrically driven film feeding mechanism for photographic apparatus



Apnl 9, 1946. E. CRONHOLM 2,398,133

ELECTRICALLY DRIVEN FILM FEEDING MECHANISM FOR PHOTOGRAPHIC APPARATUSFiled April '15, 1944 3 Sheets-Sheet l INVENTOR.

BY wxzwffipm.

ATTORNEY.

April 9, 4 E. CRONHOLM 2,398,133

ELECTRICALLY DRIVEN FILM FEEDING MECHANISM FOR PHOTOGRAPHIC APPARATUSEther cm;

ATTORNEY.

IN VENTOR.

April 9, 1946."

CRONHOLM 2,398,133

I :5 Sheets-Sheet s INVENTOR.

zwzw 75-23%;

ATTORNEY.

Patented Apr. 9, 1946 ELECTRICALLY DRIVEN FILM FEEDIN G MECHANISM FORPHOTOGRAPHIC APPA- RATUS Einar Cronholm, Goteborg, Sweden ApplicationApril 13, 1944, Serial No. 530,887 In Sweden May 8, 1942 4 Claims. (Cl.242-7 1) In a photographic apparatus for single exposures wherein theroll film feeding mechanism is driven by an electric motor it isimportant that the rotating element from which the movement for feedingthe film is taken is brought to stop exactly after each completedrevolution. For this purpose it has been proposed to transmit themovement from the motor by means of a disengaging coupling whereby meansare provided for disengaging the driven element of the coupling after acompleted revolution of said element.

The main object of this invention is to provide a film feeding mechanismof the kind referred to which operates satisfactorily even underdisadvantageous conditions, for instance at the low temperatures towhich cameras for photographing from aircraft (aerial cameras) areexposed.

An embodiment of the invention is shown in the accompanying drawings,wherein:

Figure 1 is a diagrammatical View of the principal parts of a takingcamera provided with a film feeding mechanism according to theinvention,

Figures 2-4 show the film feeding mechanism in different operatingpositions, and

Figure 5 is a plan view of the disengaging coupling.

In Figure 1, in which the casing of the taking camera and the bearingsfor the several shafts and axis are removed, A denotes the shutter and Bthe film which is wound off from the spool C to the take-up spool Dfixed to the rotatably mounted shaft E. This shaft E by means of a bevelgear system F is driven by a rotatably mounted shaft I. G indicates anelectrical motor which by means of a worm gear G rotates a rotatablymounted shaft H provided at one end with a bevel gear wheel 6. To theshaft I there is fastened a circular disc 2 in the periphery of whichthere is provided a recess 3. On the shaft I adjacent to the disc 2there is rotatably mounted a ratchet 4 which by means of a sleeveconnected to a bevel gear wheel 5 meshing with the aforesaid bevel gearwheel 6 is caused to rotate therewith. At the same side of the disc 2 asthe ratchet 4 there is provided a pawl 8 swingably mounted on a journal1 fixed to the disc, said pawl being actuated by a spring 9 which aimsto swing the pawl into engagement with the ratchet 4. The pawl isprovided with a curved tail portion III which extends to the recess 3.On a rotatably mounted shaft II parallel to the shaft I there isswingably mounted a radially projecting arm I2 which at its free end isprovided with a nose I3. The arm I2 is actuated by a cylindrical spiralspring I4 surrounding the shaft II the one end of said spring beingfastened to a pin I5 projecting from the arm I2 and parallel to theshaft II. The other end of the spring I4 is fastened to a pin I6projecting towards the arm I2 from a double arm fixed to and radiallyprojecting from the shaft II, the one branch of said double arm beingindicated by Ila and the other branch by Ilb. The pins I5, I6 limit byabutting against each other the swinging movement caused by the springI4 of the arm I2 and the double arm Ila, Ilb in relation to each other.The free end of the branch Ilb carries an abutment I8 adapted toco-operate with a cam I3 fixed to the shaft I. On the pin I5 there isswingably mounted an arm 20 adapted to operate a switch 2| in theelectric lines I to the motor G. 23 indicates a slidably mountedreleasing member adapted to co-operate with the branch Ila which isactuated by a spring 22. At the free end of the arm I2 there is provideda roller 24 adapted to actuate the tail portion III of the pawl 8.

The device described operates in the following manner:

In the initial position shown in Figure 4 and in which the arm I2 andthe double arm Ila, Ilb are kept by the releasing member 23 against theaction of the spring 22, the nose I3 of the arm I2 finds itself in therecess 3 and the roller 24 keeps by acting upon the tail portion III thepawl 3 out of engagement with the ratchet 4. In this position of the armI2 the switch 2I is kept in off position by the link 20. As thereleasing member 23 is drawn up out of engagement with the branch Ilathe spring 22 swings the branches Ila and Ilb and also the arm I2 to theposition shown in Figure 2, whereby the nose I3 of the arm I 2 isbrought out of engagement with the recess 3, the roller 24 is broughtaway from the tail portion I0, so that the pawl 8 by the spring 9 may bebrought into engagement with the ratchet 4, and the abutment I8 carriedby the branch Ilb is brought within the path of movement of the cam I9.At the same time the link 20 brings the switch to closed position sothat the motor G starts, whereb the shaft I is caused to rotate in thedirection indicated by the arrow a in Figure 2. During the revolution ofth shaft I the cam I9 swings the branch Ilb in the direction indicatedby the arrow bin Figure 2, whereby the spring I4 is keeping the arm I2against the disc 2 along the periphery of which the nose I3 of the armI2 is sliding with a pressure depending on the tension of the spring I4.Before the highest point of the cam I9 leaves the abutment I8 of thebranch H the other branch Ila has been swung away from the path ofmovement of the releasing member 23 so that this may by a spring 26 bebrought back to its arresting position shown in Figure 3. As the recess3 during the revolution of the disc 2 reaches the nose l3 sliding alongthe periphery of the disc 2 the arm I2 is permitted to be swung by thespring I4 towards the centre of the disc back to its initial position inthe recess 3 (see Figure 4), whereby the roller 24 carried by the arm 12abuts with great force against the tail portion In so that the pawl 8 isswung out of engagement with the ratchet 4. The shaft which has nowcompleted a revolution is thus stopped, and during this revolution ofthe shaft I the exposed portion of the film B has been wound up on thespool D driven by the shaft I. At the last mentioned swinging movementof the arm [2 the switch 2| is by means of the link 20 brought back toopen position, whereby the motor G will cease to rotate. The severalparts of the feeding mechanism are now ready for a further release bymeans of the releasing member 23, whereby the operation described willbe repeated.

I claim:

1. An improvement in roll film feedin mechanisms for cameras for takingsingle exposures comprising a motor driven toothed wheel, a disc havinga recess formed in the peripher thereof, a pawl pivotally mounted onsaid disc and adapted to engage said toothed wheel, a member pivotallymounted adjacent the periphery of said disc, a spring connected to saidmember for retaining the same against the periphery of said disc, an endportion of said pawl being positioned for receiving movement from saidpivotal memher when abutting said disc recess and means for operativelyconnecting said disc to the film take up spool.

2. .An improvement in roll film feeding mechanisms for cameras fortaking single exposures comprising a motor driven toothed wheel, a dischaving a recess formed in the periphery thereof,

a pawl pivotally mounted on said disc and adapted to engage said toothedwheel, a member pivotally mounted adjacent the periphery of said disc, aspring connected to said member for retaining the same against theperiphery of said disc, an end portion of said pawl being positioned forreceiving movement from said pivotal member when abutting said discrecess, means for operatively connecting said dis to the film take upspool, a cam connected to said disc and said spring for increasing thetension of said spring on-movement of said disc.

3. An improvement in roll film feeding mech anisms for cameras fortaking single exposures comprising an electric motor driven toothedwheel, a disc having a recess formed in the periphery thereof, a pawlpivotally mounted on said disc and adapted to engage said toothed wheel,a shaft, a member pivotally mounted on said shaft adjacent the peripheryof said disc, an arm projecting from said shaft, a cam connected to saiddisc and contacting said arm, a spring connecting said arm and saidpivotal member and adapted to retain said member against the peripheryof said disc, an end portion of said pawl being positioned for receivingmovement from said pivotal memher when abutting said disc recess andmeans for operatively connecting said disc to the film take up spool.

4. An improvement in roll film feeding mechanisms for cameras for takingsingle exposures comprising an electric motor driven toothed wheel, adisc having a recess formed in the periphery thereof, a pawl pivotallymounted on said disc and adapted to engage said toothed wheel, a shaft,a member pivotally mounted on said shaft adjacent the periphery of saiddisc, a switch connected in the current supply lines of theaforementioned electric motor, means operativel connecting said pivotalmember to said switch for opening said switch when said member abutssaid disc recess, an arm projecting from said shaft, a cam connected tosaid disc and contacting said arm, a spring connecting said arm and saidpivotal member and adapted to retain said member against the peripheryof said disc, an end portion of said pawl being positioned for receivingmovement from said pivotal member when abutting said disc recess andmeans for operatively connecting said disc to the film take up spool.

EINAR CRONHOLIH.

